Assessment of early osteoarthritis in hip dysplasia with delayed gadolinium-enhanced magnetic resonance imaging of cartilage

Background: The efficacy of surgical and medical treatment of osteoarthritis is difficult to assess because of the lack of a noninvasive, sensitive measure of cartilage integrity. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) was designed to specifically examine glycosaminoglycan changes in articular cartilage that occur during the development of osteoarthritis. Our primary goal was to compare this technique with measurement of the joint space width on conventional radiographs in patients with hip dysplasia. We performed this comparison by assessing the correlation between the findings of each technique and clinically important factors such as pain, severity of dysplasia, and age. Methods: Sixty-eight hips in forty-three patients were included in the study. Clinical symptoms were assessed with use of the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire. The width of the joint space as well as the lateral center-edge angle of Wiberg (as a measure of the severity of the dysplasia) was measured on standard standing radiographs. Magnetic resonance imaging maps of glycosaminoglycan distribution were made with T1-calculated images after administration of gadopentetate(2-) (Gd-DTPA(2-)). The dGEMRIC index was calculated as the average of the T1 values for the acetabular and femoral head cartilages. Results: The dGEMRIC index correlated with both pain (r(s) = -0.50, p < 0.0001) and the lateral center-edge angle (r(s) = 0.52, p < 0.0001), whereas the joint space width did not correlate with either, with the numbers available. There was a correlation between the dGEMRIC index and pain whether or not a labral tear was present. The dGEMRIC index was significantly different (p < 0.0001) among three groups of hips classified according to whether they had mild, moderate, or severe dysplasia, whereas the joint space width did not differ significantly among these three groups. There was no significant correlation between age and any of the other parameters. Conclusions: We demonstrated that, in patients with hip dysplasia, the dGEMRIC index-a measure of the biochemical integrity of cartilage-correlates with pain and the severity of the dysplasia and is significantly different among groups of hips with mild, moderate, and severe dysplasia, suggesting that it may be a sensitive measure of early osteoarthritis. Additional studies are needed to determine whether dGEMRIC can be used to predict disease progression in different situations and/or demonstrate responses to therapeutic interventions.